Zonal Boundaries Research Articles

The geochemical signatures of the Silurian–Devonian succession in eastern Saudi Arabia

This study was performed on 663 sandstone core and cutting samples taken from the Silurian?Devonian succession in five wells, located in eastern Saudi Arabia. This study aimed to correlate the Tawil Formation in the study wells, defining the lower Qalibah/ Tawil and upper Tawil/Jauf boundaries. The Tawil Formation is mostly characterized by clastic-dominated fluvial to marginal marine depositional environments. A chemostratigraphic correlation workflow was established using key element ratios and comprising four zones (C1 to C4) and five subzones (C2-1 to C2-3 and C3-1-C3-2). The chemostratigraphic zonation allowed robust characterization of stratigraphy in the uppermost Qalibah, Tawil, and lower Jauf Formations. Zone C1 is associated in most cases with the Sharawra Formation. Zones C2 and C3 are generally linked with the Tawil Formation, and Zone C4 broadly defines the lower part of Jauf Formation. In detail, the chemostratigraphic zonal boundaries do not precisely match the biostratigraphical and lithostratigraphic boundaries, indicating that the C1-C2 and C3-C4 boundaries are probably time-transgressive. The ratio Zr/Nb was used to model sequence stratigraphy. This ratio can vary in proportion to grain size, in which the element Zr is known to be concentrated in the heavy mineral zircon; while Nb-bearing heavy minerals along with clay minerals, likely illite, produce Nb. The increasing Zr/Nb ratio values are considered to define the coarsening upward or regressive sequences while decreasing Zr/Nb trends can mark fining upward or transgressive sequences.

Integrated stratigraphy at the Bartonian–Priabonian transition: Correlation between shallow benthic and calcareous plankton zones (Varignano section, northern Italy)

AbstractThe Varignano section (Trento province, northern Italy) provides an exceptional opportunity for a direct correlation between shallow benthic (SB) zones and standard calcareous plankton zones at the Bartonian–Priabonian transition (middle–late Eocene). This transition has attracted great attention by biostratigraphers in the last decades in searching for a boundary stratotype section. The Alano di Piave section (NE Italy) is the leading candidate for the base Priabonian Global Stratotype Section and Point (GSSP). However, at Alano, larger foraminifera-bearing resedimented levels occur exclusively well below the critical interval. Conversely, the Varignano section, located ∼80 km west of the Alano section, preserves several coarse bioclastic levels rich in larger foraminifera throughout the section. These levels are intercalated with basinal marlstones, crystal tuff layers, and an organic-rich interval. The Varignano section spans planktic foraminiferal Zones E10 and E11 to lower E14, calcareous nannofossil Zones MNP16Bc to MNP18 and Chrons 18n to 17n.2n. The main calcareous plankton events recently proposed as primary base-Priabonian correlation tools, i.e., the last occurrence of the genus Morozovelloides and the Base common (= acme beginning) of Cribrocentrum erbae occur, respectively, within C17n.3n and C17n.2n. We correlate prominent crystal tuff layers exposed at Varignano with those outcropping at Alano, including the Tiziano bed, whose base has also been proposed as the GSSP level. The Varignano section spans the upper SB17 and the lower SB18 Zones, with the zonal boundary marked by the first occurrence of the genus Pellatispira. This event occurs in the lower part of Zones E13 and MNP17A within C18n, well below all the potential criteria to identify the GSSP that also includes Chron C17n.1n base. We point out that the usage of shallow-water biostratigraphers in placing the base of the Priabonian at the base of Zone SB19 is inconsistent with the proposed plankton events.

Simulating Current and Future River-Flows in the Karakoram and Himalayan Regions of Pakistan Using Snowmelt-Runoff Model and RCP Scenarios

Upper Indus Basin (UIB) supplies more than 70% flow to the downstream agricultural areas during summer due to the melting of snow and glacial ice. The estimation of the stream flow under future climatic projections is a pre-requisite to manage water resources properly. This study focused on the simulation of snowmelt-runoff using Snowmelt-Runoff Model (SRM) under the current and future Representative Concentration Pathways (RCP 2.6, 4.5 and 8.5) climate scenarios in the two main tributaries of the UIB namely the Astore and the Hunza River basins. Remote sensing data from Advanced Land Observation Satellite (ALOS) and Moderate Resolution Imaging Spectroradiometer (MODIS) along with in-situ hydro-climatic data was used as input to the SRM. Basin-wide and zone-wise approaches were used in the SRM. For the zone-wise approach, basin areas were sliced into five elevation zones and the mean temperature for the zones with no weather stations was estimated using a lapse rate value of −0.48 °C to −0.76 °C/100 m in both studied basins. Zonal snow cover was estimated for each zone by reclassifying the MODIS snow maps according to the zonal boundaries. SRM was calibrated over 2000–2001 and validated over the 2002–2004 data period. The results implied that the SRM simulated the river flow efficiently with Nash-Sutcliffe model efficiency coefficient of 0.90 (0.86) and 0.86 (0.86) for the basin-wide (zone-wise) approach in the Astore and Hunza River Basins, respectively, over the entire simulation period. Mean annual discharge was projected to increase by 11–58% and 14–90% in the Astore and Hunza River Basins, respectively, under all the RCP mid- and late-21st-century scenarios. Mean summer discharge was projected to increase between 10–60% under all the RCP scenarios of mid- and late-21st century in the Astore and Hunza basins. This study suggests that the water resources of Pakistan should be managed properly to lessen the damage to human lives, agriculture, and economy posed by expected future floods as indicated by the climatic projections.

The rise of pinnacle reefs: A step change in marine evolution triggered by perturbation of the global carbon cycle

The first appearance of pinnacle reef tracts, composed of hundreds to thousands of localized biogenic structures protruding tens to hundreds of meters above the surrounding mid-Silurian seafloor, represents a step change in the evolution of the marine biosphere. This change in seafloor morphology opened a host of new ecological niches that served as “evolutionary cradles” for organism diversification. However, the exact timing and drivers of this event remain poorly understood. These uncertainties remain, in large part, due to a paucity of index fossils in the reef facies, the difficulty of correlating between the offshore pinnacle reefs and more temporally well-constrained shallow marine facies, and cryptic unconformities that separate amalgamated reefs. Here we use δ13Ccarb stratigraphy within a sequence stratigraphic framework to unravel these complex relationships and constrain the origination of Silurian pinnacle reef tracts in the North American midcontinent to near the Pt. celloni Superzone—Pt. am. amorphognathoides Zonal Group boundary of the mid-Telychian Stage.In addition, we identify a striking relationship between pulses of reef development and changes in global δ13Ccarb values and sea level. Viewed through this new perspective, we correlate prolific periods of reef development with short-lived carbon isotope (δ13Ccarb) excursions and eustatic sea level change that, ultimately, reflect perturbations to the global carbon cycle. From changes in the dominance of microbial reefs of the Cambrian to metazoan colonization of reefs in the Middle Ordovician, through the subsequent collapse of metazoan diversity with the Late Ordovician mass extinction, and the first appearance of early Silurian (Llandovery) pinnacle reef tracts and their proliferation during the late Silurian (Wenlock-Pridoli) and Devonian, major reef formation intervals increasingly coincide with δ13Ccarb excursions. These patterns suggest that Paleozoic reef evolution was the product of environmental forcing by perturbations of the global carbon cycle.

A global biogeochemical perturbation during the Middle Frasnian punctata Event: Evidence from muted carbon isotope signature in the Appalachian Basin, New York State (USA)

Abstract A modest positive stable carbon isotope excursion coincident with the Upper Devonian Middlesex Formation of western New York State and beneath the Palmatolepis transitans - Palmatolepis punctata zonal boundary is interpreted to define the beginning of the Middle Frasnian punctata Event. The broad positive excursion that defines this global isotopic event elsewhere, however, appears to have been muted in the northern Appalachian Basin by a tectonically induced regression and associated deposition of the organic-deficient Cashaqua Formation. δ13Corg increases upward through the lower two-thirds of the Cashaqua, peaking approximately 4.5 m below its contact with the overlying Rhinestreet Formation in the mid-punctata Zone. Above this stratigraphic level, δ13Corg diminishes 2.2‰ over a vertical distance of 41 cm that encompasses a newly recognized interval of microtektite-like spherules. Thus, that part of the studied section between the middle of the Middlesex Formation and the peak δ13Corg value in the upper Cashaqua Formation embraces the stratigraphic range of the punctata positive excursion dampened by the regional base level reduction and associated increased flux of 13C-depleted terrestrial weathering runoff, including dissolved inorganic carbon (DIC). δ13Corg values recover to pre-negative excursion levels through the top of the Cashaqua Formation into the lower Rhinestreet Formation. The sharp negative excursion terminating the punctata Event of western New York likely records the sudden introduction of 12C into the ocean - atmosphere system, perhaps related to destabilization of sea-floor methane hydrates. However, hydrate dissociation concurrent with rising global sea level and in the absence of a closely preceding thermal event sufficient to raise bottom-water temperature is problematic. The coincidence of the stratigraphic interval containing the microtektite-like spherules and the onset of the negative carbon isotope excursion suggests that impact-induced mechanical disruption of the ocean floor may have triggered the release of methane.

Foraminiferal biostratigraphy and paleoenvironments of the Danian-Selandian succession at the Kharga Oasis, Western Desert, Egypt

The present work deals with the foraminiferal investigations and analyses of the Danian-Selandian (D-S) succession at Naqb El-Rufuf and Umm El-Ghanayim sections in the Kharga Oasis. Five planktonic foraminiferal zones and subzones (P1c, P2, P3a, P3b, and P4a) were recognized within the studied sections. The D/S stage boundary is characterized by a faunal break at the P3/P4 zonal boundary owing to completely or partially absence of the P3b subzone. This hiatus reveals the dual signature of both the eustatic sea-level changes and the regional tectonic event of the Syrian Arc System. The studied interval is subdivided into three transgressive-regressive sequences bounded by three sequence boundaries at the Cretaceous-Paleogene (K/Pg.) boundary, the boundary between P3a/P3b subzones and the D/S boundary, respectively. The D/S transition is associated with substantial changes in the structure and composition of the foraminiferal assemblages point to extensive paleoenvironmental turnover. The latest Danian sediments were deposited under deep inner-shallow middle neritic environments with oxygen-depleted bottom water conditions and increased trophic level, where an outer neritic environment with meso-oligotrophic and well-oxygenated bottom water conditions prevailed during the deposition of the Selandian deposits.

The Paleocene/Eocene (P/E) boundary along the eastern plateau of Kharga-Baris oases, Western Desert, Egypt

Integrated high resolution calcareous planktonic nannofossil and foraminiferal biostratigraphic studies are carried out on the Paleocene/Eocene (P/E) boundary at Gebel El Aguz and Gaga on the eastern plateau of the Kharga-Baris oases, Western Desert, Egypt. The five beds of the Dababiya Quarry Member of the Esna Formation are represented partially on the study sections. At G. El Aguz beds nos. 1–4 are missing, whereas at Gaga bed no. 1 is absent which indicates the occurrence of a hiatus with different magnitude. This hiatus is documented by the occurrence of irregular surface with pebbles at G. El Aguz and the occurrence of glauconitic layers at Gaga section. Biostratigraphically, the P/E boundary is defined at the NP9a/NP9b nannofossil zonal boundary which is equivalent to the Morozovella velascoensis (P5)/Acarinina sibaiyaensis (E1) at Gaga section and A. soldadoensis/Globanomalina pseudomenardii (P4c)/A. sibaiyaensis (E1) planktonic foraminiferal zonal boundaries at G. El Aguz with interzonal hiatus. This indicates that the sedimentary basin during the P-E interval at the study area was unstable and affected by a tectonic event may be due to the echo of the Syrian Arc Orogeny.

Aalenian — Lower Bajocian (Middle Jurassic) ostracods from the Geisingen clay pit (SW Germany)

This study of ostracods from 26 samples from the Aalenian and Lower Bajocian of Geisingen (Baden-Württemberg, southern Germany) has yielded five faunal assemblages. The assemblages from the Lower Aalenian are dominated by small-sized ostracod species and are in general less diverse than those assemblages recorded from the Middle and Upper Aalenian. First order microfaunal changes occur at the base of the Lower Aalenian “Comptum” Subzone, at the Bradfordensis/Gigantea Subzonal boundary and at the Bradfordensis/Concavum Zonal boundary. A second order microfaunal change is also noted at the Aalenian/Bajocian boundary (Concavum/Discites Zones). The following new species are described: Polycope circulosa, Cardobairdia tesakovae, Cytheropterina alacostata, Cytheropterina bicuneata, Infracytheropteron bisulcatum, Procytheropteron catena, Aphelocythere dilgeri, Praeschuleridea concentrica, Pleurocythere ohmerti, Progonocythere scutula, and Kinkelinella (K.) geisingensis. 13 presumably new species of Cytherurids, 1 “Monoceratina” sp. and 1 Kinkelinella sp. as well as 6 specimens ‘incertae sedis’are figured, but left in open nomenclature. The holotype and a paratype of Polycope pelta Fischer, 1961 are figured for the first time in SEM photographs.

New age controls on Oligocene and Miocene sediments in southeastern Australia

The Cenozoic spore-pollen zonation scheme of southeastern Australia is used to constrain the ages of marine and terrestrial strata throughout Australasia. New palynological, strontium isotope and foraminiferal data from the Torquay and Gippsland basins in southeastern Australia are here used to revise and chronologically calibrate the Oligocene and Miocene portions of this scheme. The revised age assigned to the Upper Nothofagidites asperus/Lower Proteacidites tuberculatus zonal boundary is 30.5–31.2 Ma, the Lower/Middle P. tuberculatus zonal boundary is 23.03 Ma, the Middle/Upper P. tuberculatus zonal boundary is approximately 21.1 Ma and the Upper P. tuberculatus/Triporopollenites bellus zonal boundary is 17.54 Ma. This revision confirms that a near-continuous Early Miocene neritic sequence is present in the Torquay Basin. The new ages also suggest that the timing of coal seam deposition in the Latrobe Valley was episodic, rather than continuous as has previously been interpreted. We propose that abrupt changes in moisture content across seam boundaries are associated with stratigraphic gaps. The new age controls facilitate more accurate comparisons of time-equivalent paleobotanical material throughout the southern hemisphere. The refinements presented will improve future Cenozoic paleoclimatic and paleobotanical reconstructions concerning Australia, New Zealand, South America and Antarctica.

Distributed hepatocytes expressing telomerase repopulate the liver in homeostasis and injury.

Hepatocytes are replenished gradually during homeostasis and robustly after liver injury1,2. In adults, new hepatocytes originate from the existing hepatocyte pool3-8, but the cellular source of renewing hepatocytes remains incompletely understood. Telomerase is expressed in many stem cell populations, and telomerase pathway gene mutations are linked to liver diseases9-11. Here, we identify a subset of hepatocytes that expresses high levels of telomerase and show that this hepatocyte subset repopulates the liver during homeostasis and injury. Using lineage tracing from the telomerase reverse transcriptase (Tert) locus in mice, we demonstrate that rare hepatocytes with high telomerase expression are distributed throughout the liver lobule. During homeostasis, these cells regenerate hepatocytes in all lobular zones, and both self-renew and differentiate to yield expanding hepatocyte clones that eventually dominate the liver. In injury responses, the repopulating activity of TERTHigh hepatocytes is accelerated and their progeny cross zonal boundaries. RNA-seq reveals that metabolic genes are down regulated in TERTHigh hepatocytes, indicating that metabolic activity and repopulating activity may be segregated within the hepatocyte lineage. Genetic ablation of TERTHigh hepatocytes combined with chemical injury causes a marked increase in stellate cell activation and fibrosis. These results provide support for a ‘distributed model’ of hepatocyte renewal in which a subset of hepatocytes dispersed throughout the lobule clonally expands to maintain liver mass.

Use of electrical resistance tomography (ERT) for the detection of biofilm disruption mediated by biosurfactants

Inline measurement of biofilms could provide a valuable technology for water, food and bioprocessing industries to improve quality control and avoid contamination. This study presents the first use of electrical resistance tomography (ERT) to detect the removal of biofilms in a pipe. It also tests the effectiveness of sophorolipids and rhamnolipids for the disruption of Bacillus subtilis BBK006 biofilms in an industrial setting. Biofilms were grown on the inner side of a section of 1.5″ test pipe for 5 days using nutrient broth as the culture medium. After the medium was removed the test pipe was incorporated into a cleaning test circuit for the biofilm disruption experiment, where water, sophorolipids (0.4gL−1) or rhamnolipids (0.4gL−1) solutions were pumped through respectively for 30min. ERT was used as an indirect evaluation of the film disruption progression. A cleaning parameter was identified based on zonal boundary averages which successfully measured the extent of biofilm removal.

Seascape genomics reveals adaptive divergence in a connected and commercially important mollusc, the greenlip abalone (Haliotis laevigata), along a longitudinal environmental gradient.

Populations of broadcast spawning marine organisms often have large sizes and are exposed to reduced genetic drift. Under such scenarios, strong selection associated with spatial environmental heterogeneity is expected to drive localized adaptive divergence, even in the face of connectivity. We tested this hypothesis using a seascape genomics approach in the commercially important greenlip abalone (Haliotis laevigata). We assessed how its population structure has been influenced by environmental heterogeneity along a zonal coastal boundary in southern Australia linked by strong oceanographic connectivity. Our data sets include 9,109 filtered SNPs for 371 abalones from 13 localities and environmental mapping across ~800km. Genotype-environment association analyses and outlier tests defined 8,786 putatively neutral and 323 candidate adaptive loci. From a neutral perspective, the species is better represented by a metapopulation with very low differentiation (global FST =0.0081) and weak isolation by distance following a stepping-stone model. For the candidate adaptive loci, however, model-based and model-free approaches indicated five divergent population clusters. After controlling for spatial distance, the distribution of putatively adaptive variation was strongly correlated to selection linked to minimum sea surface temperature and oxygen concentration. Around 80 candidates were annotated to genes with functions related to high temperature and/or low oxygen tolerance, including genes that influence the resilience of abalone species found in other biogeographic regions. Our study includes a documented example about the uptake of genomic information in fisheries management and supports the hypothesis of adaptive divergence due to coastal environmental heterogeneity in a connected metapopulation of a broadcast spawner.

ISOLINE OF THE BORDER OF NAVIGATION SAFETY ZONE OF A VESSEL

[For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version)].ABSTRACT Prevention of the majority of emergency situations in navigation is based on observing a certain distance between vessels, which allows timely taking precautionary measures in order to avoid contact. The thus created conditional space of safety distances forms a navigation safety zone. The article gives a universal conceptual definition of such a zone, a generalized structural classification of factors affecting its size and shape, the nature of the isolinear zonal boundary. The concepts of isoasphalia as an idealized safe boundary, as well as an isoasphalic surface forming an idealized safe area around the vessel are introduced. On the basis of set theory, a variational law of variation of piecewise functions describing a safe space asymmetric with respect to the vessel’s diametric plane is derived. The resulting expression allows us to identify the boundary of an asymmetric elliptical navigation safety zone. Keywords: sea vessels, navigation safety, idealized model, isoline boundary, isoashpalia, isoasphalic surface, asymmetric elliptic zone, set theory, variational law.

Quantifying the Impact of 20-Year Flood Frequency on Land Cover Change Type

Flooding is the most common and destructive natural disaster in the United States. Ninety percent of all disasters in the US involve flooding, with impacts that cascade across the entire landscape. The primary objective of this study is to understand the impact of flooding on the landscape. One way to determine this is to observe the number of times a unit area of land is flooded and intersect that information with quantified changes in the landscape. The information for this analysis is derived from a complex workflow with inputs from large amounts of Landsat satellite imagery (more than 300 images) and multiple dates of land cover data from the USGS NLCD. The acquired NLCD data were used to generate from-to bivariate land cover change classes. A bivariate dataset was created for 5 date pair epochs. These classes were then used as zonal boundaries within which statistical variables were generated based on the flood frequency layer. By analyzing this information, we characterized what classes changed to what other classes given different frequencies of flooding. The area of interest for this study consists of one path row or footprint of a Landsat image on the border of Louisiana, Texas, and Arkansas near the city of Shreveport, Louisiana. This study area is known to have frequent flooding and a diverse landscape. During our analysis, we discovered that land cover changes in this study area more often occurred within areas that had flooded, rather than areas that had not flooded. Barren land cover change is clearly associated with flooding. Agricultural land changing to barren suggested that frequent flooding may cause arable land to not be as productive. When Barren land changes to vegetated cover and when Water changes to Barren, there is a strong likelihood that the change was due to flooding. Interestingly Urban land cover changes intersected with flood frequency regardless of the ratio. Over 2600 ha of Urban were built within the areas that have previously flooded. Some of the from-to change identified in this analysis was due to classification error, however this was minimized due to USGS’s approach to land cover classification update, whereby only areas of change are classified. The results of this analysis are very useful for identifying where land cover change areas exist, their extent, and the likelihood they are associated with flood activity. This has implications and applications to flood plain management and community land use planning. The results of this study showed there is a relationship between some land cover change types and areas that frequently flood.

On the effects of storage facilities on optimal zonal pricing in electricity markets

This paper analyzes the effects of storage facilities on optimal zonal pricing in competitive electricity markets. In particular, we analyze a zonal pricing model that comprises consumers, producers, and storage facilities on a network with constrained transmission capacities. In its two limit cases, our zonal pricing model includes the reference nodal pricing model as well as the uniform pricing model with storage. To the best of our knowledge we are the first to analyze zonal pricing in the presence of storage. As our numerical results show, storage facilities do not only reduce the inter-temporal price volatility of a market, but may considerably change the inter-regional price structure. In particular, the inter-regional price volatility may increase in the presence of storage, which may imply a complete reconfiguration of optimal zonal boundaries as compared to the no-storage case. However, market participants may have an incentive to keep or implement a sub-optimal zonal design. Thus, storage facilities will in general challenge optimal congestion management with common heuristic approaches to configure optimal price zones (e.g., the use of congested transmission lines of a nodal pricing system) not always suggesting optimal zonal configurations. Therefore, we propose a model extension that allows policy makers to determine welfare maximizing zonal configurations, which account for the complex inter-regional price effects of storage facilities. Especially with regard to increasing storage investments, such a model may help to (at least partially) handle the described inefficiency problems regarding sub-optimal zonal designs that may challenge European or Australian zonal electricity markets in the near future.

Calcareous nannofossil biostratigraphy of the Paleocene at the Misheiti section, East Central Sinai, Egypt

Integration of calcareous nannofossil data, δ13C and δ18O values, and carbonate contents of the lower Paleocene–upper Paleocene sequence that crops out at the Misheiti section, East Central Sinai, Egypt, were used to denote the Danian/Selandian (D/S) and Selandian/Thanetian (S/T) stage boundaries. The study interval belongs to the Dakhla and Tarawan formations. Four calcareous nannofossil zones (NP4, NP5, NP6, and NP7/8) were recognized. The base of the Selandian Stage is tentatively placed at the lowest occurrences (LOs) of taxa ascribable to the second radiation of fasciculiths (i.e., Lithoptychius janii). This level is marked by a sudden drop of δ13C and δ18O values and carbonate content. No distinctive lithological changes were observed across the D/S boundary at the study section. A hiatus at the NP5/NP6 zonal boundary is indicated by the condensation of zones NP5 and NP6. The base of the Thanetian is placed at the base of Zone NP7/8 at the lithological change observed in correspondence to the boundary between the Dakhla and Tarawan formations. The δ13C and δ18O values abruptly decrease slightly above the base of Zone NP7/8. No consistent variations in the carbonate contents were recorded within Zone NP6 or across the NP6/NP7/8 zonal boundary.

Ostracod assemblages from the uppermost Pliensbachian and Lower Toarcian of the Traras Mountains (Tlemcen Domain, north Algeria)

This work presents a taxonomic study of the Upper Pliensbachian-Lower Toarcian ostracods from the Traras Mountains situated in northwestern of Algeria. The ostracod fauna comprises 8 families, 11 genera and 20 species. Important changes in the composition of the ostracod assemblages have been recorded related to the Pliensbachian-Toarcian boundary and the Polymorphum-Levisoni zonal boundary (the biotic crisis related to the Toarcian Oceanic Anoxic Event). This turnover is denoted by the uppermost Pliensbachian assemblages dominated by the families Healdiidae and Cytherellidae to the upper part of Levisoni Zone with the assemblages dominated by the families Protocytheridae and Polycopidae. Ten species of ostracods are recognised for the first time from the Lower Toarcian of the North Gondwana palaeomargin (Bairdia kempfi, Bairdiacypris dorisae, B. triangularis, Ektyphocythere bizoni, Ogmoconcha convexa, Paracypris sp. and Polycope cincinnata). The comparison with other regions (intrafamilial comparison and qualitative comparison) reveals close relationships between the location of the basins and their taxonomic compositions.

Spatial externalities and land use regulation: an integrated set of multiple density regulations

In a continuous city with three distinct land use zones consisting of business, condominiums and detached houses, we derive the formulae which simultaneously optimize regulations on building size, lot size and the three zonal boundaries under the existence of agglomeration economies and traffic congestion. The formulae show that the optimal regulations require a combination of downward and upward adjustments to the market sizes of buildings within both the business zone and the condominium zone, followed by minimum lot size regulation in the housing zone. The outer boundaries of the condominium and housing zones should be regulated inward whereas the optimal business zone boundary regulation depends on the trade-off between agglomeration economies and traffic congestion costs.

The CHilean Internal Migration (CHIM) database: Temporally consistent spatial data for the analysis of human mobility

Changes in zonal boundaries and coding schemes severely compromise temporal comparison of data. In Chile, the Population and Housing census is the only comprehensive source of internal migration data, but municipal boundaries and occupation and industry sector coding schemes have undergone various changes which hamper the temporal comparability of census data. This paper presents the CHilean Internal Migration database developed by Rowe and Bell (2013) which provides a temporally consistent framework for the analysis of internal migration over a period covering twenty-five years from 1977 to 2002. Specifically, it offers a hierarchical system of 304 municipalities, 51 provinces and 13 regions, and 10 occupational groups and 11 industrial sectors which are temporally consistent over the 1977-82, 1987-92 and 1997-2002 census intervals. The database can be downloaded from: https://s3.amazonaws.com/geoda/data/CHIM.zip.

The CHilean Internal Migration (CHIM) database: Temporally consistent spatial data for the analysis of human mobility

Changes in zonal boundaries and coding schemes severely compromise temporal comparison of data. In Chile, the Population and Housing census is the only comprehensive source of internal migration data, but municipal boundaries and occupation and industry sector coding schemes have undergone various changes which hamper the temporal comparability of census data. This paper presents the CHilean Internal Migration database developed by Rowe and Bell (2013) which provides a temporally consistent framework for the analysis of internal migration over a period covering twenty-five years from 1977 to 2002. Specifically, it offers a hierarchical system of 304 municipalities, 51 provinces and 13 regions, and 10 occupational groups and 11 industrial sectors which are temporally consistent over the 1977-82, 1987-92 and 1997-2002 census intervals. The database can be downloaded from: https://s3.amazonaws.com/geoda/data/CHIM.zip.